1. Jiangsu Academy of Science and Technology for Inspection and Quarantine, Nanjing, Jiangsu 210001, PR China
2. Department of Travel Health, Nanjing Entry-Exit Inspection and Quarantine Bureau, Nanjing, Jiangsu 211106, PR China
3. Department of Ultrasound, Nanjing Hospital of Armed Police Force Corps, Nanjing, Jiangsu 210028, PR China
4. Research Institute of General Surgery, Jinling Hospital, Nanjing, Jiangsu 210002, PR China